<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .left,
        .right,
        .mid {
            /* float: left; */
            width: 100px;
            height: 100px;
        }

        .left {
            float: left;
            background-color: rgb(253, 192, 192);
        }

        .mid {
            /* overflow: hidden; */
            width: 300px;
            height: 100px;
          
            background-color: rgb(31, 86, 215);
        }

        .right {
            clear: both;
           float: right;
            background-color: rgb(54, 252, 77);
        }
    </style>
</head>

<body>
    <!-- 1.怎么实现三列布局（左侧和右侧宽度固定，中间自适应） -->
    <div class="nav">
        <div class="left"></div>
        <div class="mid"></div>
        <div class="right"></div>
    </div>
</body>

</html>